Flux modulated ringer



Aug. 23, 1955 J. R. POWER FLUX MODULATED RINGER Filed Oct. 25, 1950 mmwww mp. wlw

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GAP A/L United States Patent O FLUX MODULATED RINGER James R. Power,Chatham, N. J., assignor to Bell Teleu phone Laboratories, Incorporated,New York, N. Y., a corporation of New York Application October 25, 1950,Serial No. 191,977

Claims. (Cl. 340-387) This invention relates to electromagneticallyoperated signaling devices and more particularly to electric ringers ofthe polarized type employed in telephone systems.

It is the object of this invention to provide an improved type of ringerwhich is simple in design, compact in construction, small in size,inexpensive to manufacture and which is responsive to electric signalsof various frequencies having a minimum power input.

A further object is to provide a ringer of waterproof constructionwithout diminishing the volume of sound radiated therefrom.

These and other incidental objects have been attained in accordance witha particular feature of this invention by'the utilization of a magneticcircuit of novel configuration which lends itself to the use of apermanent magnet of small size, simple pole-pieces and a singlecoilbearing core, all combined to effect a small compact assembly whichwill function with maximum eiiiciency and high sensitivity.

A chief characteristic of an eflicient telephone ringer is that themagnetic circuit embodied therein be of such design as to permit amaximum value of flux set up by the ringing current to be effective inactuating the ringing armature. To obtain such a ringer there has beenemployed in this invention a magnetic shunt constructed of magnetic ironand interposed between the extended polepieces of the magnetic core inparallel relation to said core. Attached to this shunt is a smallpermanent magnet which extends therefrom toward the pivoted portion ofthe ringing armature. For any given half cycle of ringing current thepolarizing ux set up by the permanent magnet and the coil ilux set up bysaid current will be additive in one pole-gap and opposed in the other,thereby creating unbalanced forces which tend to rotate the ringingarmature.

In addition to the coil flux iiowing through the pole-gap, some of saidux will iiow through the magnetic shunt wherein it will add to thepolarizing flux in onedhalf of said shunt and subtract therefrom in theother half. As the shunt is so constructed that its ilux densityestablished by the permanent magnet alone is very high, changes indensity due to the coil ux flowing therethrough will substantiallychange the reluctance in the two legs of said shunt. These changes inreluctance, will in turn, destroy the symmetry of the polarizingcircuit, with the result that more of the polarizing flux will owthrough the pole-gap in which the core and polarizing iiuxes areadditive, thereby further increasing the torque tending to rotate thearmature.

An additional feature of this invention contemplates a magnetic circuitarrangement wherein the ringer may be waterproofed by enclosing thecoil, magnet and polepieces in a watertight housing, with the armature,clapper and gongs remaining outside said housing. Such an arrangementprotects the coil and electrical terminals, and at the same time permitsunrestricted radiation of the sound produced.

Still another feature of the invention which contributes materially tothe over-all objectives of smallness in size,

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increased capability and lower costs, resides in the use of a singleoperating coil.

These and other features of the invention will be readily understoodfrom the following detailed description when read in reference to theaccompanying drawings, in which:

Fig. l is a perspective view of the ringer embodying the features of theinvention, said ringer is shown partially enclosed in a waterproofhousing, a section of which has been cut away in order to show theconstruction of the ringer in greater detail;

dFig. 2 is a front plan View of the ringer shown in Fig. l; an

Fig. 3 is a schematic illustration of the magnetic circuit of the ringershowing the various ux paths set up therein.

Referring now to Figs. l and 2, mounting brackets 10 are shown as thechief support for the portion of the ringing structure which is enclosedin water-tight housing 11, and base plate 13 serves to support theportion of the ringer structure positioned outside said housing.Brackets 10 are secured to housing 11 by means of screws 12, and baseplate 13 is similarly secured by screws 14. As an alternative, brackets10 could be fastened directly to base plate 13, or made a part thereof,depending upon the need for water-tight housing 11 in any particularapplication of this ringer.

An H-shaped magnetic iron pole-piece 15, which has turned-up legs 16 and17 forming pole-faces of the operating magnetic gap, is attached tobrackets 1t) by means of screws 18. Mounted across the opposite legs ofpolepiece 15 is the electromagnet comprising coil 19 and laminatedsilicon-steel core 2t), said core being secured to pole-piece 15 bymeans of screws 21 which accommodate suitable nuts, not shown. The useof laminated silicon steel for the core, although not essential tosatisfactory operation of the ringer, reduces the eddy-current lossthereby helping to maintain a high impedance at voice frequency, adesired condition. A small permanent magnet 23 of substantially roundsection, preferably constructed of Alnico V, having its polar axis atright angles to the magentic axis of the electromagnet is placed againstVturned-up extension 22 of the cross-bar portion of pole-piece 15. Thispermanent magnet is held in place by means of crimped legs 24.

A substantially rectangular-shaped armature 25 is provided with integralbent-over extensions 26 and 27 having suitable holes which accommodatethe pivot pin 28 in such a manner as to permit the armature to rotatefreely about the pin, said pin being supported from base plate 13 bybracket 41. Armature extension 26 serves to support a clapper rod 29which is staked therein; A clapper 30 is staked to the other end of saidclapper rod and so placed that said clapper will strike gongs 31 whenarmature 25 rotates about its pivot point. Gongs 31 are mounted by meansof screws 32 into projecting portions 33 of base plate 13 which serve assupporting posts for said gongs.

A biasing spring 34 is staked to extension 27 of the armature, the freeend of which may be selectively engaged in one of several notches in theedge of plate 35 which is fastened to base plate 13. The biasing springis under such tension that when engaged in one of said notches it willexert a force on the armature tending to hold said armature at the limitof its travel in one direction. The magnitude of this force isadjustable by the selection of the notch in which the spring is engaged.The two stops 36 and 37 are attached to turned-up portions 38 and 39,respectively, of base plate 13, and are so positioned as to limit therotation of armature 25. Said stops serve as means for preventing thearmature from striking housing 11 as shown in Fig. 2. However, if theringer is operated without housing 11, then said stops are needed toprevent sticking of the armature to the polev faces.

Fig. 3 illustrates diagrammatically the magnetic ux paths of themagnetic system embodied in the ringer of this invention. The polarizingflux path, that is, the path traversed by the flux set up by permanentmagnet 23, is represented by continuous lines and the path of the fluxset up by the ringing current is represented by broken lines. The arrowheads on the continuous lines indicate the direction of the biasing huxin the circuit at all times, while the arrow heads on the broken linesindicate the direction of the ringing current flux during the half cycleof alternating current of direction indicated by the arrow heads on coil19, it being understood that the flux direction in the latter case isreversed during every half cycle of ringing current. Pole-piece 15 isrepresented for simplicity as an H-shaped section of magnetic material.The cross bar of said pole-piece will hereinafter be referred to as themagnetic shunt designated by legs D and E.

The polarizing flux emanating from the north pole N of the permanentmagnet 23 enters the magnetic shunt portion of pole-piece 15 wherein itdivides and traverses two branches: one of which includes leg D of saidshunt, air-gap A, armature 25 and thence back to the south pole S ofmagnet 23 by way of air-gap M; the second path includes leg E of saidshunt, air-gap B, armature 25 and thence back to south pole S by Way ofair-gap M. When the armature 25 is in its neutral position, that is,air-'gaps A and B being of equal length, the polarized flux distributionis symmetrical and flows along the paths previously described. Undersuch condition the ux in gap A equals that in gap B and the magneticforces in said gaps exert Y equal and opposite torques on the armaturesthereby cancelling one another.

Now assuming that a ringing current traverses coil 19 in the directionindicated, said current will cause flux to flow from core 2@ downwardinto the left leg of pole-piece 15 whence it divides, one branchfollowing a path back to the opposite end of core 20 through air-gap A,armature 25, air-gap B and the right leg of pole-piece 15. This coil uxwill be additive to the polarizing flux in gap A and opposed to thepolarizing flux in gap B. The torques in gaps A and B will, therefore,be unbalanced tending to rotate the armature in a clockwise directionabout its midpoint so as to actuate said ringer.

In addition to the above-described path some coil flux will ow throughthe shunted portion DE of pole-piece 15 in a direction `from left toright, assuming the current in coil 19 is as indicated, this ux ybeingadditive to the polarizing flux lin leg E and opposed to the polarizingiiux in leg D. Pole-piece 15 should be so constructed that the fluxdensity in shunt DE is of high magnitude due to the polarizing ux of-permanent magnet 23 alone. This is accomplished by constricting thecross-section of said shunt to the extent that the flux density in theshunt is far above the knee of the saturation curve. If the shunt is notso kconstricted a greater portion of coil flux will pass through saidshunt rather than through the pole-gaps. With pole-piece 15 properlydesigned the changes in density due to the coil flux will cansesubstantial changes in the reluctance of the two legs: increasing in Eand decreasing in D. These changes in reluctance will, in turn, destroythe symmetry of the polarizing ux circuit, and as a result more of saidpolarizing ux will ow through gap A and less through gap B. The net eectof this shift in polarizing flux is to further increase the torquetending to rotate the armature. This flux modulation feature has beenfound to substantially increase the force factor of said armaturethereby producing a more etiicient ringer.

It should be apparent that during the following half cycle of ringingcurrent the polarity of coil flux will be opposite to that hereindescribed so that the fluxes will be additive in air-gap B, therebytending to rotate armature 25 in a counter-clockwise direction, and soon during succesive half cycles of alternating current.

AIt is to be understood that the form of this invention, herewith shownand described, is to be taken as a preferred example of the same, andthat various changes in the shape, size and arrangement of parts may beresorted to, without departing from the scope of the invention.

What is claimed is:

l. A magnetic circuit comprising a coil, a core having one section onwhich said coil is mounted and provided at each end with polar extensionof magnetic material projecting at right angles to the coil-mountingsection of said core, an armature pivotally mounted at its center witheach of its ends disposed in spaced relation to a different one of ythepolar extensions of said core, a shunt of magnetic material couplingsaid polar extensions, and a bar-type permanent magnet contiguouslyassociated with said magnetic shunt and disposed in spaced relation tosaid armature midway of the ends thereof and with its polar axis atright angles to the longitudinal axis of said armature.

2. A polarized electromagnetic device comprising a coil, a core on onesection of which said coil is mounted, pole-pieces of magnetic materialfixed to said core and extending at right angles from the ends thereof,a shunt of magnetic material disposed between said pole-pieces, apivotally mounted armature bridging said pole-pieces and adapted topivot about a center transverse axis thereof, and a straight bar-typepermanent magnet having its polar and longitudinal axes coincident, saidmagnet having one end in fixed abutting relation to said shunt andprojecting therefrom in a direction such that the enter transverse axisabout which said armature pivots is located on the polar axis of saidpermanent magnet.

3. A polarized electromagnetic device comprising a coil-bearing corehaving one of a pair of parallelly disposed members of magnetic materialprojecting in the same direction from each of the ends of said core toeffect a substantially U-shaped element, a magnetic shunt memberparallelly disposed with respect to said coilbearing core and joiningsaid parallelly disposed members intermediate the free ends thereof andthe said coilbearing core, an armature spanning the free ends of saidparallelly disposed members and pivotally mounted at its center point inspaced relation to the free ends of said parallelly disposed members toeffect a pair of airgaps, .and a bar-type permanent magnet having oneend in fixed abutting relation with said shunt member substantially atits center and the other end in alignment with the free ends of saidparallelly disposed members and in spaced relation to the center pointof said armature whereby the polarizing flux produced by said permanentmagnet traverses two separate paths each including one of said air-gapsand a substantially half-section of said shunt member and in which saidhalf-sections the polarizing flux travels in opposite directions.

4. The combination of a watertight housing and a telephone ringerconsisting of two independent unit assemblies, one of said assembliescomprising a magnet core having pole-pieces, a coil mounted on said coreand a permanent magnet, the other of said assemblies comprising anarmature, a pair of gongs and a clapper supported by said armaturebetween said gongs, means removably mounting said rst assembly whollyWithin said housing and means removably mounting said secondassemblyexteriorly of said housing.

5. The combination defined in lclaim 4 in which the said ringerassemblies are so relatively disposed that the pole-pieces of theinteriorly mounted assembly are magnetically coupled with the armatureof the exteriorly mounted assembly through a wall of said housing.

References Cited in the tile of this patent UNITED STATES PATENTS353,274 Tucker et al. Nov. 23, 1886 530,253 Worley Dec. 4, 1.894 881,539Bliss Mar. l0, 1908 (Other references on following page) UNITED STATESPATENTS Reeve Dec. 9, 1913 Butte Jan. 14, 1919 Fussner June 12, 1923Feder Jan. 21, 1930 5 Carpenter Oct. 13, 1931 Miller Oct. 4, 1949FOREIGN PATENTS Great Britain of 1894 Great Britain of 1914 GreatBritain Sept. 27, 1917 Great Britain Jan. 17, 1940 Switzerland Sept. 1,1945

